Low-temperature sintered microwave dielectric ceramic material and preparation method thereof

Abstract

The invention discloses a low-temperature sintered microwave dielectric ceramic material and a preparation method thereof, and belongs to the technical field of electronic materials. The composite material comprises the following raw materials: CaCO3, SrCO3, Bi2O3 and B2O3. The preparation method comprises the following steps: burdening and weighing according to a stoichiometric ratio CaxSr1-xBi2B2O7 (x is more than 0.1 and less than 0.9), then carrying out ball milling and mixing, pre-sintering to obtain pre-sintered ceramic powder, adding an organic material to prepare stable slurry, carrying out tape casting to obtain a green body, and sintering to obtain the low-temperature sintered microwave dielectric ceramic material. The sintering temperature of the ceramic material is 700-800 DEG C, the dielectric constant range is 4-8, the loss value is less than 0.00002, and the ceramic material has low dielectric constant and ultrahigh quality factor. The problems that an existing low-temperature sintering microwave dielectric ceramic material is high in water absorption and high in material cost are solved. The microwave ceramic dielectric is applied to the technical field of electronic components requiring low dielectric constant and low loss value microwave ceramic dielectric.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic materials, and more particularly to the technical field of microwave dielectric ceramic materials. Specifically, it relates to a low-temperature sintering microwave dielectric ceramic material and a preparation method thereof. Background Art

[0002] In recent years, with the continuous development of technology, electronic components have been developing towards miniaturization and integration. LTCC (Low-Temperature Co-Fired Ceramic) plays an important role in the electronic field. LTCC, which stands for Low-Temperature Co-Fired Ceramic, is a technology of electronic components with an integral structure formed by combining multiple ceramic layers and conductive layers and sintering at a relatively low temperature (≤960°C). This special preparation process enables the LTCC technology to maintain the high-temperature resistance, insulation performance or dielectric characteristics of ceramic materials while achieving good functionality, realizing the advantages of dense functional components and miniaturized dimensions.

[0003] Typical commercial LTCC materials are mainly divided into three categories: glass-ceramics, ceramic / glass, and low-fire ceramics. However, most of the currently used low-dielectric-constant LTCC substrate materials have a dielectric constant in the range of 5.00 - 8.00, and most of them are developed for microwave low-frequency applications and rarely involve millimeter-wave applications. The development trend of LTCC materials for future millimeter waves is to have a lower dielectric constant (ε = 1 - 8) at high frequencies, a suitable dielectric loss (tanδ < 0.001), that is, a high quality factor (Q×f) value, and a near-zero resonance frequency temperature coefficient (τ f = ±10 ppm / °C). Low-fire microwave dielectric ceramic materials have very little or even zero glass phase content in their microstructures. This type of system can retain the original microwave dielectric properties to the greatest extent while meeting the requirements of low-temperature co-firing. Therefore, the characteristics of low or no glass phase determine the good high-frequency characteristics of this system. Although there are few commercial applications at present, it is still the most promising candidate material for high-frequency applications of microwave millimeter waves.

[0004] Glass-free LTCC material systems usually use low-melting-point oxides or fluorides as sintering aids, or even some ceramic material systems with intrinsic low-fire or ultra-low sintering temperatures. In the oxide system, ceramic families such as silicates, vanadates, antimonates, molybdates, and germanates generally have the characteristics of low dielectric constant and high Q×f values. However, ceramic materials such as vanadates, antimonates, and molybdates have extremely strong water absorption, which seriously inhibits commercial applications. Germanates have extremely high material costs, significantly increasing the actual production cost and resulting in an increase in the final application cost.

[0005] In view of this, the present invention is specifically proposed. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to solve the problems of strong water absorption and high material cost of existing low-temperature sintering microwave dielectric ceramic materials.

[0007] To this end, the present invention provides a low-temperature sintering microwave dielectric ceramic material, and the composition raw materials include: CaCO3, SrCO3, Bi2O3, B2O3, and weighing is carried out according to the stoichiometric ratio Ca x Sr 1-x Bi2B2O7 (0.1 < x < 0.9).

[0008] The purity of the CaCO3 is ≥99.9%, and the particle size is 0.8 μm ± 0.2 μm; The purity of the SrCO3 is ≥99.9%, and the particle size is 1.1 μm ± 0.2 μm; The purity of the B2O3 is ≥99.9%, and the particle size is 0.9 μm ± 0.15 μm; The purity of the Bi2O3 is ≥99.9%, and the particle size is 1.4 μm ± 0.2 μm.

[0009] The preparation method of the low-temperature sintering microwave dielectric ceramic material is as follows: a. Weigh the raw materials CaCO3, SrCO3, Bi2O3, B2O3 according to the stoichiometric ratio Ca x Sr 1-x Bi2B2O7 (0.1 < x < 0.9); b. Place the weighed raw materials, alumina ball milling beads, and deionized water in a nylon ball milling tank according to the set mass ratio, ball mill and mix, dry the slurry and sieve it; c. Heat the powder obtained in step (b) in the air at a set heating rate to a set temperature and keep it warm; d. Ball mill and mix the powder obtained in step (c) again, dry it and sieve it to obtain a powder; e. Add the powder obtained in step (d) to one or more of the organic materials such as anhydrous ethanol, xylene, butyl acetate, isopropanol, polyoxyethylene alkylphenol ether, polyvinyl butyral, and acrylic resin in a set mass ratio, and ball mill and disperse it to form a stable slurry; f. Cast the slurry obtained in step (e) to obtain a film (green body) with a set thickness; g. Obtain a square piece with a set size and thickness by laminating and isostatic pressing the film obtained in step (f); h. Screen print a layer of silver paste with a set thickness on the film obtained in step (f), and obtain a square piece with a set size and thickness by laminating and isostatic pressing; i. Sinter the flakes obtained in steps (g) and (h) in air to obtain a microwave dielectric ceramic material (ceramic flakes) with low-temperature sintering.

[0010] The microwave ceramic material of the present invention has a low dielectric constant and a low loss value, can be compatible with silver electrodes, has a low dielectric constant, an ultra-high quality factor, and a low sintering temperature (700°C - 800°C). The dielectric constant ε ranges from 4 to 8, and the loss value < 0.00002.

[0011] The microwave ceramic material of the present invention has low water absorption, low material cost, and low process cost, solving the problems of strong water absorption and high material cost of existing low-temperature sintering microwave dielectric ceramic materials.

[0012] It can be widely applied to the technical field of electronic components that require microwave ceramic dielectrics with low dielectric constants and low loss values. Description of the Drawings

[0013] Figure 1 Schematic diagram of the scanning electron microscope effect of co-firing with silver electrodes in Example 3.

[0014] Figure 2 Schematic diagram of the physical effect of the microwave dielectric ceramic substrate obtained in Example 3. Detailed Embodiments

[0015] As Figure 1 shown, the specific embodiments of the low-temperature sintering microwave dielectric ceramic material and its preparation method are as follows: Case 1: The preparation method of the low-temperature sintering microwave dielectric ceramic material is as follows: a. Weigh the raw materials CaCO3, SrCO3, Bi2O3, and B2O3 according to the stoichiometric ratio of Ca 0.2 Sr 0.8 Bi2B2O7. b. Place the weighed raw materials in step (a), alumina ball milling beads (the diameter of the ball milling beads is 1 mm), and deionized water in a nylon ball milling tank according to a mass ratio of 1.6:10:3, ball mill and mix for 24 hours, with a rotation speed of 400 revolutions per minute. Dry the slurry and pass it through a 120-mesh sieve. c. Heat the powder obtained in step (b) in air at a heating rate of 0.5°C / min to 550°C and hold for 4 hours. d. Ball mill and mix the powder obtained in step (c) again for 48 hours, dry it, and pass it through a 60-mesh sieve to obtain a powder. e. Add the powder obtained in step (d) to absolute ethanol with a mass ratio of 28% - 40%, polyoxyethylene alkylphenol ether with a mass ratio of 1% - 3%, and polyvinyl butyral with a mass ratio of 28% - 40%, and ball-mill and disperse for 48 hours to obtain a stable slurry; f. Cast the slurry obtained in step (e) to form a film with a thickness of 0.1 mm - 0.6 mm; g. Subject the film obtained in step (f) to laminated isostatic pressing to obtain a square piece with a size of 65 mm × 65 mm and a thickness of 1 mm - 2 mm; h. Screen-print a layer of silver paste with a thickness of 5 μm - 40 μm on the film obtained in step (f), and subject it to laminated isostatic pressing to obtain a square piece with a size of 65 mm × 65 mm and a thickness of 1 mm - 2 mm; i. Sinter the square pieces obtained in steps (g) and (h) in air, with an air flow rate of 1 L / min - 4 L / min, heat up to 550°C at a rate of 0.2°C / min, hold for 4 hours, then heat up to 700°C - 800°C at a rate of 2°C / min, hold for 30 minutes, and then cool down to 500°C at a rate of 3°C / min, and then cool with the furnace to room temperature to obtain a microwave dielectric ceramic material with low-temperature sintering.

[0016] Case 2: Weigh the raw materials CaCO3, SrCO3, Bi2O3, and B2O3 according to the stoichiometric ratio Ca 0.4 Sr 0.6 Bi2B2O7, and the other steps are the same.

[0017] Case 3: Weigh the raw materials CaCO3, SrCO3, Bi2O3, and B2O3 according to the stoichiometric ratio Ca 0.6 Sr 0.4 Bi2B2O7, and the other steps are the same.

[0018] Case 4: Weigh the raw materials CaCO3, SrCO3, Bi2O3, and B2O3 according to the stoichiometric ratio Ca 0.8 Sr 0.2 Bi2B2O7, and the other steps are the same.

[0019] The performance comparison table of specific implementation cases is shown in Table 1.

[0020] Table 1 Performance Comparison Table of Examples 1 - 4 Example Sintering Temperature (°C) <![CDATA[Dielectric constant ε r > Loss Whether Compatible with Silver Electrode 1 760 4.3 0.000016 Compatible 2 760 4.8 0.000013 Compatible 3 760 5.1 0.000011 Compatible 4 760 5.8 0.000013 Compatible It can be seen from Table 1 of the performance comparison of implementation cases that all implementation cases have low dielectric constants and low loss values, and can be compatible with silver electrodes. The SEM effect of the co-firing of Example 3 with silver electrodes is as Figure 1 shown. There is no reaction or diffusion between the ceramic and the electrode, and the physical effect of the microwave ceramic material obtained by sintering is as Figure 2 shown.

[0021] Finally, it should be noted that the above embodiments are only examples for clear illustration. The present invention includes but is not limited to the above embodiments, and it is not necessary and impossible to enumerate all implementation manners here. For those of ordinary skill in the art, other different forms of changes or variations can be made on the basis of the above description. All implementation manners that meet the requirements of the present invention belong to the protection scope of the present invention.

Claims

1. A low-temperature sintering microwave dielectric ceramic material, characterized in that: The raw materials include CaCO3, SrCO3, Bi2O3 and B2O3, according to the stoichiometric ratio of Ca x Sr 1-x Bi2B2O7 is weighed; The value range of x is: 0.1 < x < 0.9; The purity of the CaCO3 is ≥99.9%, and the particle size is 0.8μm ± 0.2μm; The purity of the SrCO3 is ≥99.9%, and the particle size is 1.1μm ± 0.2μm; The purity of the B2O3 is ≥99.9%, and the particle size is 0.9μm ± 0.15μm; The purity of the Bi2O3 is ≥99.9%, and the particle size is 1.4μm ± 0.2μm.

2. The preparation method of a low-temperature sintering microwave dielectric ceramic material according to claim 1, characterized in that The preparation method is as follows: a. Weigh the raw materials CaCO3, SrCO3, Bi2O3, and B2O3 according to the stoichiometric ratio Ca x Sr 1-x Bi2B2O7 (0.1 < x < 0.9). b. Place the raw materials weighed in step (a), alumina ball milling beads, and deionized water in a nylon ball milling tank according to the set mass ratio, ball mill and mix, dry the slurry and sieve it; c. Heat the powder obtained in step (b) in air at the set heating rate to the set temperature and hold for a certain time; d. Ball mill and mix the powder obtained in step (c) again, dry it and then pass it through a sieve to obtain a powder; e. Add one or more of the organic materials such as absolute ethanol, xylene, butyl acetate, isopropanol, polyoxyethylene alkylphenol ether, polyvinyl butyral, and acrylic resin with a set mass ratio to the powder obtained in step (d), ball mill and disperse it to form a stable slurry; f. Cast the slurry obtained in step (e) to form a film with a set thickness; g. Subject the film obtained in step (f) to laminated isostatic pressing to obtain a square piece with a set size and thickness; h. Screen-print a layer of silver paste with a set thickness on the film obtained in step (f), and subject it to laminated isostatic pressing to obtain a square piece with a set size and thickness; i. Sinter the square pieces obtained in steps (g) and (h) in air to obtain a low-temperature sintered microwave dielectric ceramic material.

3. The preparation method of a low-temperature sintered microwave dielectric ceramic material according to claim 2, wherein: The sintering temperature of the microwave ceramic material is 700°C to 800°C, the dielectric constant is 4 to 8, and the loss value < 0.00002.

4. The preparation method of a low-temperature sintering microwave dielectric ceramic material according to claim 2, characterized in that, The specific preparation method is as follows: The preparation method of a low-temperature sintered microwave dielectric ceramic material is as follows: a. Weigh the raw materials CaCO3, SrCO3, Bi2O3, and B2O3 according to the stoichiometric ratio Ca x Sr 1-x Bi2B2O7 (0.1 < x < 0.9). b. Place the raw materials weighed in step (a), alumina ball milling beads (the diameter of the ball milling beads is 1mm), and deionized water in a nylon ball milling tank according to the mass ratio of 1.6:10:3, ball mill and mix for 24 hours, the rotation speed is 400 revolutions per minute, dry the slurry and pass it through a 120-mesh sieve; c. Heat the powder obtained in step (b) in air at a heating rate of 0.5°C / min to 550°C and hold for 4 hours; d. Ball mill and mix the powder obtained in step (c) again for 48 hours, dry it and then pass it through a 60-mesh sieve to obtain a powder; e. Add absolute ethanol with a mass ratio of 28% to 40%, polyoxyethylene alkylphenol ether with a mass ratio of 1% to 3%, and polyvinyl butyral with a mass ratio of 28% to 40% to the powder obtained in step (d), ball mill and disperse for 48 hours to obtain a stable slurry; f. Cast the slurry obtained in step (e) to form a film with a thickness of 0.1mm to 0.6mm; g. Subject the film obtained in step (f) to laminated isostatic pressing to obtain a square piece with a size of 65mm × 65mm and a thickness of 1mm to 2mm; h. Apply a layer of silver paste with a thickness of 5 μm to 40 μm on the diaphragm obtained in step (f), and obtain a square piece with a size of 65 mm × 65 mm and a thickness of 1 mm to 2 mm through laminated isostatic pressing; i. Sinter the square pieces obtained in steps (g) and (h) in air. The air flow rate is 1 L / min to 4 L / min. Heat up to 550 °C at a rate of 0.2 °C / min, hold for 4 hours, then heat up to 700 °C to 800 °C at a rate of 2 °C / min, hold for 30 minutes, and then cool down to 500 °C at a rate of 3 °C / min, and then cool to room temperature with the furnace to obtain a low-temperature sintered microwave dielectric ceramic material.

5. The preparation method of a low-temperature sintering microwave dielectric ceramic material according to claim 4, characterized in that: When x = 0.2 and the sintering temperature is 760 °C, the dielectric constant is 4.3 and the loss value is 0.000016.

6. The preparation method of a low-temperature sintering microwave dielectric ceramic material according to claim 4, characterized in that: When x = 0.4 and the sintering temperature is 760 °C, the dielectric constant is 4.8 and the loss value is 0.000013.

7. The preparation method of a low-temperature sintering microwave dielectric ceramic material as described in claim 4, characterized in that: When x = 0.6 and the sintering temperature is 760 °C, the dielectric constant is 5.1 and the loss value is 0.000011.

8. The preparation method of a low-temperature sintering microwave dielectric ceramic material according to claim 4, characterized in that: When x = 0.8 and the sintering temperature is 760 °C, the dielectric constant is 5.8 and the loss value is 0.000013.

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